Debt of Blood
by L. VanDattae
Summary: Subaru never meant to hurt anyone, least of all the kind stranger he met in the woods, but now the stranger has invited him to stay. Permanently. And freeing him might be more than Kamui can handle. AU. Sei/Su, Fu/Kam


**Disclaimer:** All characters are copyright of CLAMP. No monetary profit is being made from the writing or distribution of this fic.

**Chapter 1**

Dangerous Encounters

When Subaru awoke to find the beautiful stranger draped in bloodless unconsciousness across his lap, he couldn't remember what had happened. Oh, he remembered going for a walk alright—remembered standing there as the stars twinkled overhead and the night air dragged its cold fingers through his hair. He even remembered the startled gasp that was torn from his lungs as a hand was placed suddenly on his shoulder. There might have been a gentle voice, asking something… But that was all. From the moment the man had touched him to the time he came back to himself, there was nothing. And suddenly he was terrified. Terrified for the man, lying there so pale. Terrified of himself—of the inexplicable loss of control. Terrified it could happen again. Terrified of the intense… _hunger _he still felt for the stranger, gnawing at him from the inside out.

He held the man close, clinging to him, wanting him desperately to wake up, to be okay. He tried again, frantically, to think back, but the last few minutes of his memory were a blur, a storm of sensations, indistinct. When he closed his eyes, out of the misty muddle of his mind, he almost remembered words… faint flickers of kind smiles…

"_It's late to be out here alone…_"

"_Are you lost?_"

He was shaking when he took the man's cool hand and fumbled for a pulse. So cold. So still. That skin against his fingertips. Shame suffused his cheeks at the thought of what he'd done, and he let the guilt worm its way inside him. A worried little frown pulled at the corners of his mouth, but it lifted into relief to feel the flutter of a pulse still moving within that lithe body. Tentatively, he traced one of those blue strands that twined up the man's arm, just visible under the skin. Kissed it. Content now that he knew the man would live, Subaru gave into the temptation to touch. To feel. To reassure himself with his hands and his lips and his skin that this kind stranger was going to be okay.

Gently at first, he brushed thick strands of black hair away from shuttered eyes, smoothed over dark eyebrows, traced the bridge of a nose. The lightest of curious touches. Then more fervently, pressing his hands wide against the broad chest, the set of firm shoulders, moving slowly to slide along the column of the man's neck. Enraptured, Subaru leaned down, pressing hesitant kisses to the tip of the chin, underneath, lower—wholly caught up in exploration, in the feel of that toned skin against his lips. If he tasted it, would it taste like bronzed sunlight? He opened his mouth…

…and jerked back, horrified by what he'd been doing.

What was _wrong _with him?

He'd almost killed the man! Again! Such… blind hunger wasn't like him. It was frightening, the effect the man had on him—the way his very proximity could make him forget all his inhibitions. He almost thought he was going mad—that this was the final descent into insanity that claimed so many of their kind. Or maybe…

Occasionally he'd heard rumors of humans whose blood called to a single vampire more strongly. Before, it had always seemed like some paltry excuse made up to shun the responsibility of senseless killing. "I couldn't help it! It was the human!" Anyway, if the rumors were true—and staring at the beautiful man sprawled out in his lap, Subaru had to admit he was running out of other explanations… if they were true, they had never really managed to effectively convey how strong the pull was. He hadn't been prepared. That's what had done him in. The intensity of it had caught him unaware.

Sure, he'd known better than to forego meals (a thing his brother, Kamui, was always pestering him about), but it wasn't like he was some fledging totally unable to decline any temptation on two legs that walked by. And he'd thought he was alone. Everything should have been fine. There was no way he could have known. He was used to the hunger, it had never been that bad, as if he'd taken a physical blow to the head, the suddenly redoubled pain leaving him dazed and disoriented, like a deer in the headlights, able to see the crash coming but too surprised to fight it.

Sudden movement jerked him out of his thoughts as the man on his lap stirred. Smiling sadly, he brushed fingers through that thick black hair one last time, laid the man down on the soft grass… and hid. It was better, really, if he wasn't there when the man woke up. Safer. So he watched from a distance as eyelashes flicked open, looking around a bit disoriented at first. Watched as the beautiful stranger climbed slowly to his feet… and then he followed him home.

Just to be safe of course. After all that blood loss, it wasn't safe to be walking around so soon. So Subaru stayed, guarding him through the rest of the night.

Of course, that didn't explain why, two nights of self-inflicted abstinence later, he had returned to the man's home, perched precariously on the little three-inch ledge outside his window—a feat quite impossible if he'd been human. And even he, with his superior balance, had one nimble foot pressed painfully against the side trim and the other hanging awkwardly over the edge in order to stay in place. But despite the awkward position, he managed to look comfortable.

The man had been on his mind almost constantly since their first meeting, always hovering on the edge of his thoughts, driving him to distraction. Even now, he wasn't sure why he'd come, what strange connection made him seek the man out. Had it been the memory of sweet blood that had driven him to the man's home, subconsciously determined to finish what it had started? Or had he purposely starved himself knowing all along where he was going, in a half-realized attempt at punishment? The Hunger was a physical thing—a deep-rooted agony, licking at his core, burning in his blood. It hurt, but then, he deserved the pain. After what he'd done to the man, it was fitting that he should suffer too. And anyway, the unsettled, sickening pangs of guilt that twisted inside him were far worse. So he stayed, perched where he was on the window, watching the man silently through the glass and feeling the hunger seethe inside him, determined that watching over the one who made the hunger burn that bright be his punishment for the night. As long as there was a nice, solid slate of glass between them, he needn't worry about hurting the man again.

For a moment the moon broke through the roiling mass of clouds above and glared across the window. He paid it no mind, just pressed his hands to the cold window pane, as though he could reach through the glass and into the dark room beyond, where, when the glass wasn't washed white with moonlight, the man's sleeping figure could just be seen on the bed. He glanced away for a few seconds to stare up at the moon contemplatively. It would be daylight soon. The time had dwindled away while he sat there, and it seemed stiflingly short. He would have to leave soon.

Caught up in his thoughts, he was startled when, in those few seconds he was turned away, the window he was leaning against was very suddenly thrown open. Caught off guard, he tumbled through the opening with a single, surprised gasp… right into a solid set of arms. They closed around him, dragging him backward into the room as surely as a riptide drags under a drowning swimmer. And the man's scent was so close now, pressed up against him, the smell of his blood worse than the weight of any water, burning in his lungs, suffocating him. Suddenly the little punishment he'd seen fit to inflict on himself of fasting for the past two days straight seemed a very bad idea, and the only thing that stopped him from losing himself again was the memory of what had happened last time…

Then he was slammed into a wall, his head cracking against it sharply, and pinned there by his throat, toes straining to reach the ground, and he couldn't break free, and he wasn't sure if it was because the man was just that strong, or because everything inside him rebelled against the thought of hurting the man again. Maybe both.

"Well, well, come to finish what you started?" And the voice was pleasant even while choking him to death. "How long have you been spying on me? Did _she_ send you?" But Subaru was beyond the ability to reply, feet slipping helplessly against the wall. For one wild second he thought he might suffocate, and thought, if that were so, it was fitting that his death be at the hands of the one he'd almost killed. Maybe it was the resigned way he didn't try to fight back, or maybe the sheen of acceptance in emerald eyes, but the man released him all of a sudden, letting him drop to the floor. Subaru gasped in air and coughed, but made no move to touch his bruised throat.

"I didn't mean… to hurt you…" he choked, crystalline tears lacing black lashes. "I'm sorry. I just… wanted to make sure you were safe."

"_You_ didn't mean to hurt _me_, huh? How… kind of you." The man's lips curled into an ironic smile, and he reached down and caught the boy's wrist, suddenly jerking Subaru to his feet, amused by the startled cry it produced. It really was a beautiful sound. One he'd have to find ways to produce more often. "But what if_ I_ mean to hurt _you_?"

"I…" Subaru tried to form coherent words—tried to drag a reply from his muddled mind—but he couldn't focus. The man was intoxicating… a slow, heady drug that Subaru was powerless to fight, much to his dismay. And trapped against him, unable to escape, Subaru found his willpower disintegrating… The worst part was the man seemed to enjoy watching his internal conflict… watching him lose the battle and slowly lean closer and closer into his embrace…

But Subaru was saved from trying to come up with a coherent reply, because at that point they were interrupted by a voice yelling through the closed bedroom door.

"Nii-san? You awake? It's almost time to leave! We'll be late!"

Catching that delicate chin in a strong grip and jerking that pretty face up to meet his, the man adopted an apologetic air. "It seems I can't play with you right now. But…" Suddenly Subaru found himself shoved brutally backward, through a door and down into a five-foot-square space.

"I'm afraid… I don't think I'll let you go…" And the door shut with a firm click, plunging the closet into absolute darkness.

* * *

The sun was still up, hanging heavily in the sky, when Seishirou returned—a fact he'd been counting on. He was pretty sure the… guest he'd acquired earlier would be trapped until sundown. He'd have liked to have stayed home that day to make sure, but some family obligations couldn't be put off (Setsuka would kill him if she found him skipping lessons). At least he'd been able to use the breaks to do some research (and thankfully no one had pestered him about the oddity of the subject).

Vampires, Seishirou mused, thinking of the piles of useless books he'd left for the librarians to put away, were not a subject he'd ever thought he'd pursue. They were not something he'd ever thought he'd _need_ to pursue. Certainly, he hadn't expected the sad, green-eyed boy he'd met wandering in the woods to have such a wicked bite…

Opening the closet door, careful not to let any stray beams of late sunlight slip past (it would be a shame to burn that fair skin), he found his guest curled cutely in the corner, bound inescapably in enchanted sleep. For a few minutes, as the dusty daylight was slowly smothered behind him, Seishirou watched the shadows shift over a small hand fisted fretfully in front of a pretty mouth… watched them tangle in the long lashes of closed eyes and slide finally away over the gentle curve of a hip and one extended leg. His little guest was quite lovely. On a whim, while the boy was still unconscious, he reached out to brush bits of black hair behind dainty ears. It was just as he was tracing the crescent curve of lashes, feeling them feather finely against his thumb, that the rosy rays of light finally snuffed out around the curve of the world and brilliant emerald eyes fluttered open. They stared at him for a heart's beat, blinking fuzzily, then suddenly flew wide with recognition as the boy jerked back, one hand coming up to cover his mouth in terror. Seishirou scowled at this reaction. Quick as a flash, he snatched one thin wrist before it could be twisted away and slowly but surely began pulling his prey in.

"No, please…" the boy pleaded, squirming helplessly, and there was more… fright in those eyes than necessary.

"Is my touch so repulsive?" Seishirou asked dispassionately, amber eyes going flat and dull. Fed up with the boy's struggles, he snaked an arm around the slim waist and dragged the boy into his arms, trapping him. Only then, with that lithe little body pressed painfully to his and one hand spread flat against the boy's stomach, feeling each panicked rise and fall of breath under his palm, did he realize just how thin that waist was. He frowned as he traced the faint ridges of protruding ribs, fingers skimming over silken skin. The boy was practically starving.

"How long has it been since you ate anything?" he asked harshly. Green eyes turned away in shame, staring guiltily at the floor. Dissatisfied, Seishirou caught the boy's chin in a bruising grip and jerked those emerald eyes back to him. Demanding. "How long?"

"Three days…"

It didn't take Seishirou long to figure out what the boy's last meal had been and why he had jerked away, panicked at being so close to a human. Really, the boy was impossible.

"What's your name?" he prodded, gentler this time, loosening his grip slightly to allow the pretty little thing to breathe easier.

"Subaru." A miserable squirm accompanied the confession.

"Subaru…" Seishirou repeated, noting the fine shudders that racked the delicate body in his arms as he stroked one fine-boned cheek, contemplating their problem. "Sakurazuka Seishirou." It wouldn't do for his guest to starve. With clinical detachment, he nicked his wrist and held it out so the blood was plainly visible, running down his hand.

"Is this what you want?" he purred, amused by the little whimpering noise he'd managed to extract and by the boy's obvious distress. There was something very pleasing in being able to produce such an effect in such a beautiful creature—to know that those anguished, emerald eyes wanted him, needed him. "Drink it."

Trembling head to toe in an attempt to stave off the twin fangs of hunger and physical agony, Subaru finally took the man's offered arm and lapped at the blood running down the fine fingers, dripping from the curled knuckles. Desperate, contented mews resonated in his throat, escaped before he could contain them, and hating himself, he bit into the man's wrist with a choked sob. As the warm blood filled his mouth and he clung to that arm with shaking hands, tears caught in the tattered lace of his lashes, splashed onto the bloodied wrist, where they ran palest pink. Tears of relief for the release from the hunger. Tears of self-loathing for causing this man further pain. Until finally he was sobbing too hard to swallow, choking and crying, the world a crystalline blur, still clinging to that arm like it was a lifeline.

A sudden sifting of fingers through his hair startled him, and the sobs abruptly cut off, swallowed in stillness. Slowly, shyly, he turned wide, green eyes on the man, watching him warily as those fingers traced the contours of his face and slid along the line of his throat, finally brushing over blood-stained lips.

"Are you afraid?"

"Please," he whispered, lips feathering against those fingers as he spoke. "Please, let me go. Kamui will be wo– " But he was silenced by a hand clamped over his mouth.

"Hush…" Seishirou told him, other hand sliding possessively from the boy's hip up along the supple back. He didn't care about any of the boy's relations and found the boy's worry for them… displeasing. One way or another, the pretty little thing was going to belong to him. "You're mine. Forget the others. I found you. You belong to me."

Silenced by the man's hand, Subaru could only stare at him pitifully.

Something silver around the boy's neck caught Seishirou's attention, and he reached out to tug at it, to pull it into the light, managing to glimpse a long silver chain before Subaru pulled it hurriedly away from his curious touches, letting it slide back down beneath his shirt.

Seishirou smiled disarmingly at the flustered expression on the boy's face and stood up. It didn't matter. He knew what it was. Even without seeing it, he knew…

Sitting down on the bed, he stretched out his hand, beseeching.

"Sakurazuka-san…" the boy began uncertainly.

"Seishirou, please," he replied.

"Seishirou-san… I really should be getting home…"

"Enough!" Annoyed, Seishirou reached out and jerked him upright, letting the forward momentum topple the boy into his arms. "I don't… care… about this _Kamui_… Forget about him. He doesn't matter." And as off-balance as the boy was, it was easy to drag him up onto the bed and shove him down on top of the blankets.

"Se-Sei…!"

"Shh." Seishirou hushed him, and, wrapping an arm around that slim waist, chained him to his side until the squirming subsided into defeat. Of course, he knew that wasn't going to be the end of it.

The problem, he realized, was that he was used to sleeping at night, while Subaru was perfectly awake, not that he was worried about the boy hurting him. On the contrary, he was pretty sure the boy's guilt would keep him in line just fine. Rather, it was the little matter of making sure he didn't escape. There were spells on the windows and doors preventing anyone but Seishirou opening them, but it was best to make sure they were going to hold against something stronger than a human. After a few minutes, he closed his eyes and quieted his breathing and waited for the boy to slip out of his arms. It didn't take long, once Subaru thought him asleep. It was impossible to hear the boy's footsteps, as hard as he listened, but he could make out other noises: the quiet clink of the doorknob, the creak of wood and window being tested, careful little sounds. Of course, there was no way out. And soon enough there was a whisper of displaced air—a sigh—as the boy came to his own understanding about just how permanent his place in the room was going to be. Seishirou smirked silently as he felt the bed shift slightly under light weight and the comfortable warmth of another body curling up, resigned, beside him again.

As he drifted off to sleep for real, he ignored the hot splashes of quiet tears along his arm.

* * *

Later that day, Seishirou watched the golden squares of sunlight slide across the floor and vanish into the darkness with annoyance. His little guest would be waking up soon. But there was nothing he could do. Setsuka had requested his presence in particular (a bothersome fondness of hers), and there was no denying Setsuka. If he refused to go, she'd simply make time for an 'inspection' of their house, and then she might find certain things hidden in his closet that he had no desire she find. Seishirou thought he should be glad that at the very least Setsuka hadn't yet dragged Fuuma into their silent struggle. Especially since, the last time they'd openly fought, she had pinned him to the floor again, just like every time before, if with a little more hassle as of late. She was still stronger than him… for now.

He smiled humorlessly at his reflection in the window. The newly-acquired little pet back at home would have to wait until later. It wasn't like he was worried about the boy escaping. Even if he managed to get through his wards, Seisirou was… assured the boy would return to him.

Thoughtfully, he fingered the silver chain around his neck.

The Seishirou in the window mirrored the movement, a reflected pair of amber eyes smiling coldly. Then he turned away. After all, Setsuka would be there soon…

* * *

Several miles away, another boy crouched, hidden by the shadows that clung to his dark clothing and by the dense foliage, and stared warily at the double-story house before him. He'd spent the night before, when his brother had failed to return, fretfully pacing and staring worriedly at the door. At first, he'd told himself it was an accident, and that Subaru had simply gotten distracted and hadn't realized what time it was. But when he'd failed to return the second night… Kamui had realized he couldn't afford to wait any longer. Something was wrong.

He'd tracked Subaru's scent back to the house before him, which seemed to indicate that, so far, Subaru had come of his own volition. But for one reason or another, his brother hadn't come back out. Mouth set resolutely, he slunk along the edge of the woods until he found a place to cross safely to the base of one smooth wall.

Someone was going to learn tonight not to mess with his twin.

Slipping in through an unlatched window—an open invitation, he mused—he landed deftly in the room on the other side, soft as a sigh. For a moment, he stood there, soft-soled feet buried in carpet, listening intently. There were two soft heartbeats coming from the second story. Instinct directed him, and he glided up the stairs, turning left at the top and walking until he found himself confronted with an obstacle in the form of a very solid door. Unlike the window, the door refused to open. He tried slipping a long nail into the crevice to coax the lock loose, but it wouldn't budge. Trying to crush the lock or claw through the door did no good either. Frustrated, Kamui kicked the thing, realizing with growing irritation that it must be spelled…

"Can I help you?" Kamui jerked around with a startled gasp, only to find his escape route blocked by a tall figure leaning lazily against the wall, small, round shades resting lightly on the bridge of his nose. By the amused smirk painted across thin lips, the man was fully aware that he had Kamui cornered and was enjoying the boy's predicament immensely. Kamui cursed himself for being so focused on the dumb door that he hadn't heard the man come up behind him. Stupid. He crouched, prepared to defend himself… or to spring forward into an attack.

"Give me back my brother!" The words ripped from his throat, angry and desperate.

"Oh?" the stranger chuckled, one eyebrow raised questioningly. "Has nii-san been causing trouble again?" Kamui shook his head, not about to trust this strange man who had Subaru locked in his house.

"Let my brother go!" He lunged forward, foot coming up and around lightning-quick. Too fast for any ordinary human to avoid. The man was going to learn that cornering an angry vampire was a very bad idea. So Kamui was very unprepared when the stranger ducked his kick and shoved him suddenly backward, thrusting him up against the door. Kamui blinked, stunned into stillness by the realization that he was pinned. _He _had been pinned! By a human!

"You should be more careful," the man chided, taking advantage of Kamui's shock to playfully tap the vampire's nose. "You might hurt someone."

Kamui wasn't listening. Now that they were so close, he was suddenly acutely aware of the man's scent rising around him, strong and heady. The ground seemed to wash out from under him. For a moment he bobbed breathlessly between waves, each pained gasp crashing down over his head, pulling him further under, until the tide caught him, and he was swept away in the current of the all-too-pleasant aroma swirling about him. Some fuzzy, distant part of his mind registered that the man had leaned forward, so that he was whispering seductively into Kamui's ear.

"What will you give me if I help you free your brother?"

It took a second for the words to have any meaning, and even then they seemed inconsequential, drowned out by the much more dominant desire licking at the inside of his skull. He wondered, dazedly, when he'd stretched up, arching back into the man's hold, hands grasping the lapels of a half-open shirt. What had he come here for again? It was lost in the vibrant thrumming of the man's blood, beating in his ears, under his lips. He opened his mouth…

And with a sudden shock of clarity, he realized the position he was in, how close he'd come to losing himself. Shutting his mouth with a sharp snap that startled the body pressed so close to his, Kamui took a deep breath… held it… and even in the impossibly small distance between them, his long nails were suddenly pressed threateningly against the man's neck.

"You'll be lucky if I leave you your life…" He shook with the knowledge of how close he'd already come… He had to get away—away from that place, away from that scent that was stealing his sanity. The man was too close. Too close!

"Ah, but if you kill me, how will you get your brother out then? You can't open the door, can you?" The man's smirk was definitely way too confident, Kamui decided. He shoved unhappily at the lithe body that was pinning him to the solid wood of the door, knowing that distance was vital to control, but it was a weak attempt, half wanting to push him away, half wanting to drag him closer.

"What do you want?" he asked finally, glaring.

"Hmm…" Gold eyes sparkled with amusement. "How about one night? From sunset to sunrise spent with me…"

"Ugh. Never!" Kamui shoved harder, and this time the man released him.

"Your choice." He shrugged. "Have fun freeing your brother." With that he turned and started walking away, unconcerned. Watching his retreating form, Kamui felt desperation threaten to choke him.

"Fine! But only one night! And I'll be late so I can eat before I come." He huffed, hating the fact that he needed this man… and that the man knew it.

"Well, in that case…" The stranger turned again and reached past him, all in one swift move. Kamui tensed visibly, an automatic response to the man's proximity and the perceived threat, but when the expected attack never came and the door started to give behind him, he relaxed minutely. "Oh, but…" the man continued, holding the door stationary with Kamui stuck in the middle for just a second longer, "there'll be no need to eat. I'll provide food…" A flash of that tell-tale smirk. Then he swept past the frozen vampire, leaving Kamui rediscovering how to breathe and staring after him, wondering if the man was completely sane. Or maybe he just didn't realize what he was talking to. Surely that had to be it.

Realizing he was being left behind, Kamui hurried after him.

* * *

**Author Note:** I'm posting this here at the request of my beta, who for some reason really likes this story. I've been dancing around crossovers before, but this is the first story that definitely has characters from both TRC and X simultaneously. At least, I don't remember Setsuka being in TRC. And it's possible there'll be other X characters at a later date. Of course, it's AU either way. I never know what to do with these stories!

If you find any mistakes, PLEASE let me know!


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